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3D printing comes to micro-sized objects

Researchers at the Vienna University of Technology have created a 3D printer that quickly prints objects on the order of microns in size. The device relies on a technique called two-photon lithography. The 3D printer uses a liquid resin that is hardened by a focused laser beam guided through the resin by scanning mirrors. The result is a hardened line of solid polymer a few hundred nanometers wide.

“Until now, this technique was quite slow,” says Jurgen Stampfl from the Institute of Materials Science and Technology at TU Vienna. “The printing speed used to be measured in millimeters per second. Our device can do 5 meters in 1 second.”

To be able to hit such speeds, the steering mechanism of the mirrors had to improve, says Stampfl. The mirrors are continuously moving during the printing process, so their acceleration and deceleration must be precise to generate high-resolution results at record-breaking speeds.

Chemistry was also important. “The resin contains molecules which are activated by laser light,” says Stampfl. “They induce a chain reaction in other components of the resin, so-called monomers, and turn them into a solid.” These initiator molecules only activate when they absorb two photons at once, which happens in the center of the laser beam where its intensity is highest. In contrast to conventional 3D printing, the new technique can create solid material anywhere in the liquid resin rather than only on top of the previously created layer. Therefore, the working surface needn’t be specially prepared before the next layer is formed, which saves a lot of time. A team of chemists led by Robert Liska at TU Vienna developed the special resin.

Researchers are now developing biocompatible resins that can be used to create scaffolds to which living cells can attach themselves, allowing the systematic creation of biological tissues.